Means for measuring the margin of operation of telegraph circuits



Feb. 8, 1927.

R. E. PIERCE MEANS FOR MEASURING THE MARGIN'OF OPERATION OF TELEGRAPH CIRCUITS Filed Nov 20. 1924 INVENTOR ficfrfi ATTORNEY Patented Feb 3, 1927.

1 or {half-duplex. system, operation,

ternal causes. circuit; has been set up in the morning for -thedays traffic and has been properly .balanced it maydater ,1 mitter 5121f the same said receiving relay.

RALPH E. PIERCE, OFLARGHMONT,

NEW YORKfASSXGNOR TO 'AM EEICAN' TELEEHONE AND'TELEGRAPH"COMPANY, ACORPOBATION"OF"NEW 'YORK.

MEANS FOR MEASURING THEMAERGIN OFlOIERATION-OF TEDEGB'ATEH'CIRGUITS.

App1ication-fi1ed .Novembcr 20, 1924. --Se1 ia1 No. 751,143.

f'lhis invention relates to electrical -measuring systems-and particularlyto means for imeasuring the range ,of current through j-Which the receiving relay of a telegraph system will operate .undervarious line conditions.

After a telegraph circuit, such as, a duplex has been set up for -:'t has been 'found-difiicult at times t -maintain the. stability of operation of {511Gb .system owing to "effects produced upon the circuit either -,-by internal or ex- Thus, for i example, after a be found that due to a change in the llne insulation the-circuit is a not balanced and the receiving relay .Will ,be

sentout by the transarmature moves toitslower contact the ,con-' 1 denser will be discharged through the gal- ,vanoineter 13. When a steadily recurring signal .is impressed upon the relay the,ar.mature-Willfollow the signal causing the conaffected' by current end-iof the line as the While various devices have been-produced -fon measuring line ,balance,,speed of; failure and other factors in connection with tele- ;;:graph 5 circui s, cletermine-the limits iOIE current within which .a rcceivingrelay 3 none QQIE .,these 7 measure -or will operate to correctly retransmitthe signalingv impulses from the line. circuit -to: the loop or terminal circuit ,With wvhich theasaid receiving relay as connected.

It 1 is the obj eetwof this invention to measure the'margin ofoperation of telegraph circuits.

1 This invention Will be'app arent from the ;following descriptioirwvhen read: in connection ,withthe attached drawing, .of which Figure '1 shows, schematically a formeof-the invention in which the -margin -of operation is determined by varying the current through the;-recei-ving relay until. failure of 5 the saidrelay to f translate ,signals is indi- --ca ted =by afailure-Ineter; Figqlshows a form of the invention operating-ion the same principle as Fig. -1,-.but em:ploying a. slightly ;diflerent-type--of calibratedshunt in which the shunt element is in, parallel with" thereceiving relayand ammeter. only; and Fig. 3

:shoWs the -application .of the invention-to a differential relay.

In; the arrangement shown in :Fig. ,1- the ;1zine-; L;is terminated by two bridged polar duplex eircuits.

'- thee-rati nn tlan l Qtheape c w c :is: connected:thesarmature, of thatrzansmit- 5 At station A this comprises of {their setting .the impedance :of athe tea tinggpole changer 3. Across the outercnds of-the ratimarms the FGCGAVIIlg HJICl measursing apparatus is connected. :This comprises the polarized receivingarelayvt, :havingh n iseries therewith a variable --re'si-stance;-R which 1S7 one of the elements ,of a universal shunt, and a variable resistance ii -which is the-aother elementof; the shunt, connected in parallel with the relay tand-theresist- Abata complete charge from the .battery .14. (hen ..the

denser; to be charged by the "source 114:, .and

thenodischarging'it throughthe,galvanoin-v eter 18. Under such condition theneedle I of the galvanolneterwill beimovedzto a. certain point upon its scale and will rem-aintat that point so long as the armature ,of the relay follows the recurring ,si-gnal.

Since any failure of theaarmature to so :act willzbe manifested a falling .back=- o-fthe ggal'vanometer needle, 1 the; l, arrangement constitutes a simple and. effective means for edetermining a when the relay fails to follow the. signals. Ill-his arrangement, which, per -se,

formsrno part of. the vinvention is disclosed in theoopendingapplication of; H. ,Nyquist,

Serial No. ,a27,9)3, filedDccemberiQ, 1,920. The line L and-its. corresponding artificial line AL, are likewise connected -.Witli the I V outer ends of thetarms leand 2. V

At station .the terminal ap-paratusis substantially that normally .used \in -a bridged duplex circuit comprising ratio arms-5 and A6, a receiving relay'andg-a balancing artificial line. ,Gonnected with the .aapexa of pole changer7. ,This rpole changer has con-W nected therewith Ta--, device. 8 for sendinga recurring .si I al such, ,for example, as the vletter 1 C. II e resistances nR- and; R at.,station are so proportioned that regardless the arms-5iand -6 is a transmitting ininal circuit is substantially unchanged. It willof course be apparent that variations in the setting of these resistances will change the magnitude of the current flowing through thereceiving relay 4, without appreciably changing the magnitude or wave shapeof the current in the line. A preferred form of shunt is one in which bOt-lh resistances may be varied by the same control mechanism to automatically keep" the impedance constant, Furthermore, if the shunt is so calibrated as to indicate the current flowing through the relay, the meter 17 maybe dispensed with.

The manner in which the circuit described above functions; to measure the margin of operation of therelay 5i is as follows: A

"recurring'signal is transmitted by the pole changer 7 over the line L, the: transmission being controlled-by the device 8. r The current representing the signals will flow through the terminal circuit at station A to ground at the artificial line AL The magnitude of the current through the branch that includes the, receiving relay 4.

.willbe determined by the setting of the resistanc'es R and R Starting with the resistances set at the points which produce the maximum current flowthrough the relay 4, which will be evidenced bythe maximum defiectionl'of the ammeter 17 or by the scale 7 of the shunt the setting 'otthe resistances before.

is varied until the current through the relay 4 has been reduced to, a value so low that the relay-fails to reproduce accurately the received signal which will be indicated by the galvanometer 13, as described herein- The arrangement shown gives a positive indication ofthe margin of operation of the relay 4: in response to signals transmitted to it over the line L from the distantstation. This, result may be. compared with the results when different conditions exist on the same circuit as, for example, whenan intermediate composite set has been inserted in'the circuit or when the line isunbalanced by'adjusting the artificial line AL .The shunt may be calibrated to indicate directly the magnitude of the current flowing through the receiving relay circuit when failureoccurred.

The arrangement shown in Fig. 2 dili'ci's only structurally from that shown in Fig.

1. In Fig. 2 the receiving relay 4 is connected across the outer ends of the arms 1 and 2 in series with the variable resistance R and a milammeter 17 A second variable resistance R is connected across only the relay 4 and the ammeter 17. The arrangement of Fig. 2 operates in substantially the same way as that shown in Fig. l. curring signal would be transmitted over the line L and the setting ofthe resistances R and R would be varied until the point is reached where the relay i'ceases to re- A re '18 to the resistance R In like manner the winding 19 is connected Wltll the artificial line'AL through the resistance R and the latter winding and resistance are shunted by the resistance R sistances during the time of reception o'l. signals from the line L the current through of course varying the impedance of the terminal circuit. The margin of operation oi this relay may'thus be determined.

In Figs. '2 and 3, for purpose of simplicity, I have omitted a representation of the armature and the failure-meter comprising the condenser, source of current and galvanometer but it is to be understoodthat such elements form a part of these circuits and that they would be connected therein in substantially the same manner in which they are connected with the circuit constituting Fig. 1. p

i It will be seen that by means of the ar rangements shown in figures of the drawing the margin of operation of a receiving relay of any type in a system adaptedeither for duplex or half-duplex operation may be By varying these rethe differential relay may be varied without ice quickly and accurately determined. The

simplicity of the arrangement combined with the fact that the impedance of the line is not varied during the course of measurement. renders the invention particularly useful in making routine maintenance tests upon telegraph systems.

lVhile the invention has been disclosed as embodied in certain particular"forms'it is of course capable of embodiment in other forms without departing from the spirit and scope of the appended claims. i

What is claimed is: V I

'1. In a system for deierii'iiniiig the margin of operation of a'telegraph circuit, the

coinbiiiationwith a source of signaling current of a terminal circuit having a receiving relay, a universal shunt controlling the current flowing through said relay and means to indicate failure of said relay to respond to the current as thus controlled.

2.111 a system for determiningt-he marginofvoperation of a telegraph circuit, the combination with a source of signaling current of a terminal circuithaving a receiving relay,- means to vary the current through the said relay without substantially changing the impedance of the terminal circuit, and

means to indicate failure of said relay to respond to the current as thus controlled.

3. In a system for determining the margin of operation of a telegraph circuit, the combination with a source of signaling current arranged to transmit a steadily recurring signal, of a terminal circuit to which said signaling current is applied, the said terminal circuit comprising a receiving relay responsive to said current, a universal shunt to vary said current without substantially changing the impedance of the said terminal circuit and means to indicate failure of said receiving relay to retransmit signals.

4;. In a system for determining the margin of operation of a telegraph circuit, the combination with a line circuit of a terminal circuit having means for applying a signaling current to the said line circuit, and a second terminal circuit having a receiving relay a universal shunt and means to indicate failure of the said relay to translate signals according to the said signaling current.

5. In a system for'determining the margin of operation of a telegraph circuit, the combination with a line circuit of a duplex terminal circuit having means for applying .a steadily recurring signal to the said line circuit for transmission thereover, and a V second duplex terminal circuit having a receiving relay, a universal shunt to vary the current through the said relay Without substantially changing the impedance of the terminal circuit, and means to indicate the failure of the said relay to translate said recurrlng signal.

6. The method for determining the margin of operation of a telegraph circuit which through or over a medium a current repre-' senting a steadily recurring signal, receiving the said current and varying the portion thereof flowing through a responsive device without substantially affecting the impedance of the receiving circuit, and indicating the margin of operation of the responsive device.

In testimony whereof, I have signed my name to this specification this 18th day of November, 1924. c

' RALPH E. PIERCE. 

